1. Field of the Invention
The present invention relates to a rocker assembly of a strapping machine, especially to a rocker assembly that automatically adjusts engagement between teeth panels and a wrapping strap according to thickness of the wrapping strap.
2. Description of the Prior Art(s)
A strapping machine straps packaged goods with steel or plastic wrapping straps so the strapped goods are convenient to transport.
With reference to FIG. 16, a conventional strapping machine comprises a tensioning wheel 91 and a rocker 92. The tensioning wheel 91 is driven by a power device to rotate in a specific direction and has multiple engaging teeth 911 formed around a peripheral surface of the tensioning wheel 91. The rocker 92 is pivotally mounted on the conventional strapping machine and has a pivoting end 921, a swinging end 922 and a teeth panel 93. The pivoting end 921 is pivotally mounted on the conventional strapping machine. The swinging end 922 moves forwards or backwards relative to the peripheral surface of the tensioning wheel 91 as the rocker 92 swings. The teeth panel 93 is embedded in the rocker 92, is disposed adjacent to the swinging end 922 of the rocker 92 and has an upper surface and multiple engaging teeth 931. The upper surface of the engaging teeth panel 93 is concave and corresponds to the peripheral surface of the tensioning wheel 91. The engaging teeth 931 of the teeth panel 93 are formed on the upper surface of the teeth panel 93 and correspond to the engaging teeth 911 of the tensioning wheel 91. Preferably, the teeth panel 93 may comprise multiple sub-panels having upper surfaces with different slopes.
A wrapping strap 94 is wrapped around the goods and has a tightening end 941 and a fixed end 942. The fixed end 942 and the tightening end 941 overlap. Then the fixed end 942 and the tightening end 941 are placed between the tensioning wheel 91 and the teeth panel 93.
With further reference to FIG. 17, the rocker 92 is driven to swing toward the tensioning wheel 91 to allow the engaging teeth 911 of the tensioning wheel 91 to engage the tightening end 941 of the wrapping strap 94 and the engaging teeth 931 of the teeth panel 93 to engage the fixed end 941 of the wrapping strap 94. When the tensioning wheel 91 is rotated, the tightening end 941 of the wrapping strap 94 is moved while the fixed end 942 of the wrapping strap 94 is held by the teeth panel 93. As the wrapping strap 94 is properly tensioned, a welding device of the conventional strapping machine welds the overlapping tightening and fixed ends 941, 942 of the wrapping strap 94 so the wrapping strap 94 is wrapped around the goods.
However, in the above-mentioned conventional strapping machine, the teeth panel 93 is securely mounted on the rocker 92. Therefore, when the teeth panel 93 and the tensioning wheel 91 engage the wrapping strap 94, the teeth panel 93 is unable to move relative to the rocker 92 according to thickness of the wrapping strap 94 to securely hold the wrapping strap 94. Thus, engagements between the teeth panel 93 and the wrapping strap 94 and between the tensioning wheel 91 and the wrapping strap 94 are loose. Consequently, the wrapping strap 94 is unable to securely wrap around the goods. Furthermore, since the tensioning wheel 91 does not securely hold the wrapping strap 94, when the tensioning wheel 91 rotates, the engaging teeth 911 of the tensioning wheel 91 scratch the wrapping strap 94 easily.
With further reference to FIG. 18, in view of the disadvantages of the foregoing conventional strapping machine, a rocker 95 of another conventional strapping machine has a pivoting end 952, a mounting recess 953, a bottom, a through hole 954, a teeth panel 96 and a bolt 97. The mounting recess 953 is formed in an upper surface of the rocker 95 and is disposed adjacent to the pivoting end 952 of the rocker 95. The bottom of the rocker 95 is defined in the mounting recess 953. The through hole 954 is formed through the bottom of the rocker 95. The teeth panel 96 is mounted in the mounting recess 953 of the rocker 95 and has a toothed upper surface 961 and a convex lower surface 962. The bolt 97 is mounted through the through hole 954 of the rocker 95 from a lower surface of the rocker 95, is attached to the teeth panel 96 and is thinner than the through hole 954 of the rocker 95 so the bolt 97 is slidable in the through hole 954 and the teeth panel 96 slides as well. When a tightening end and a fixed end of a wrapping strap are mounted between the teeth panel 96 and a tensioning wheel 98, the convex lower surface 962 of the teeth panel 96 allows the teeth panel 96 to swing and to slightly slide. Thus, angle and position of the teeth panel 96 can be adjusted according to thickness of the wrapping strap and the tensioning wheel 98 so the wrapping strap is securely held by the teeth panel 96 and the tensioning wheel 98.
However, since the teeth panel 96 of the above-mentioned conventional strapping machine is formed in a single piece, when the teeth panel 96 swings, only part of the toothed upper surface 961 engages the wrapping strap. Engagement between the teeth panel 96 and the wrapping strap is still loose and the wrapping strap drops out of the rocker 95 and the tensioning wheel 98 easily.